Pressed component manufacturing method, pressed component, mold, and press apparatus

ABSTRACT

A pressed component includes an elongated top plate; ridge line portions at both short direction ends of the top plate; and vertical walls that face each other in a state extending from the ridge line portions, and the top plate includes a minimum portion, at which the Vickers hardness value is a minimum value, between one end and another end in the short direction of the top plate, and maximum portions, at which the Vickers hardness value is a maximum value, in each of a first range between the minimum portion and the one end, and a second range between the minimum portion and the other end.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of copending U.S. patent applicationSer. No. 15/567,652, filed Oct. 19, 2017, which is the National Phaseunder 35 U.S.C. § 371 of International Application No.PCT/JP2016/062681, filed on Apr. 21, 2016, which claims the benefitunder 35 U.S.C. § 119(a) to Japanese Patent Application No. 2015-087502,filed in Japan on Apr. 22, 2015, and Japanese Patent Application No.2015-087503, filed in Japan on Apr. 22, 2015, all of which are herebyexpressly incorporated by reference into the present application.

TECHNICAL FIELD

The present disclosure relates to a manufacturing method for a pressedcomponent, a pressed component, a mold, and a press apparatus.

BACKGROUND ART

Automotive bodies are assembled by superimposing edges of multipleformed panels, joining the formed panels together by spot welding toconfigure a box body, and joining structural members to requiredlocations on the box body by spot welding. Examples of structuralmembers employed at a side section of an automotive body (body side)include side sills joined to both sides of a floor panel, an A-pillarlower and an A-pillar upper provided standing upward from a frontportion of the side sill, a roof rail joined to an upper end portion ofthe A-pillar upper, and a B-pillar joining the side sill and the roofrail together.

Generally speaking, configuration elements (such as respective outerpanels) of structural members including A-pillar lowers, A-pillaruppers, and roof rails often have a substantially hat-shaped lateralcross-section profile configured by a top plate extending in a lengthdirection, two convex ridge line portions respectively connected to bothsides of the top plate, two vertical walls respectively connected to thetwo convex ridge line portions, two concave ridge line portionsrespectively connected to the two vertical walls, and two flangesrespectively connected to the two concave ridge line portions.

SUMMARY OF INVENTION Technical Problem

The configuration elements described above have comparatively complexlateral cross-section profiles and are elongated. In order to suppressan increase in manufacturing costs, the above configuration elements aregenerally manufactured by cold pressing. Moreover, in order to bothincrease strength and achieve a reduction in vehicle body weight in theinterests of improving fuel consumption, thickness reduction of theabove structural members is being promoted through the use of, forexample, high tensile sheet steel having a tensile strength of 440 MPaor greater.

However, when a high tensile sheet steel blank is cold pressed in anattempt to manufacture configuration elements that curve along theirlength direction, such as roof rail outer panels (referred to below as“roof members”; roof members are automotive structural members),spring-back occurs during removal from the press mold, leading toconcerns of twisting in the top plate. There are therefore issues withshape fixability, whereby roof members cannot be formed in a desiredshape.

For example, Japanese Patent Application Laid-Open (JP-A) No.2004-314123 (referred to below as “Patent Document 1”) describes aninvention in which a pressed component having a uniform hat-shapedlateral cross-section along its length direction is applied with a stepduring manufacture in order to suppress opening-out, and thus improvethe shape fixability.

Moreover, the specification of Japanese Patent No. 5382281 (referred tobelow as “Patent Document 2”) describes an invention in which, duringthe manufacture of a pressed component that includes a top plate,vertical walls, and flanges, and that curves along its length direction,flanges formed in a first process are bent back in a second process soas to reduce residual stress in the flanges, thereby improving the shapefixability.

According to the invention described in Patent Document 1, whenmanufacturing pressed components having a shape that curves along thelength direction, such as in configuration elements of configurationmembers such as A-pillar lowers, A-pillar uppers, or roof rails,spring-back occurs in the top plate after removal from the mold, suchthat the desired shape cannot be formed.

According to the invention described in Patent Document 2, whenmanufacturing pressed components that curve along the length directionand height direction and that include a bent portion in the vicinity ofthe length direction center, residual stress arises in the flange,residual stress arises within the faces of the vertical walls and thetop plate, and residual deviatoric stress arises within the faces of thevertical walls and the top plate. As a result, spring-back occurs in thetop plate after removal of the press component manufactured according tothe invention described in Patent Document 2 from the mold, such thatthe desired shape cannot be formed.

An object of the present disclosure is to provide a manufacturing methodfor a specific pressed component in which the vertical walls aresuppressed from closing in due to spring-back. Note that in the presentspecification, a “specific pressed component” is a pressed componentconfigured including an elongated top plate, ridge line portions at bothshort direction ends of the top plate, and vertical walls that face eachother in a state extending from the ridge line portions.

Solution to Problem

A manufacturing method for a pressed component of a first aspectaccording to the present disclosure is a manufacturing method for aspecific pressed component. The manufacturing method includes employinga die and a punch to bend a blank into a profile protruding from thepunch side toward the die side in a state in which a punch is caused tocontact a first portion of the blank where the two end ridge lineportions are to be formed, and to sandwich a second portion of the blankwhere the top plate is to be formed between the die and the punch, andindent the second portion from the die side toward the punch side.

A manufacturing method for a pressed component of a second aspectaccording to the present disclosure is a manufacturing method for aspecific pressed component, wherein a punch and a die are employed tobend a blank from the punch side toward the die side in a state in whichthe punch is caused to contact a first portion of the blank where thetwo end ridge line portions are to be formed, and to sandwich a secondportion of the blank where the top plate is to be formed between the dieand the punch and indenting the second portion from the die side towardthe punch side such that the second portion has a radius of curvature R(mm) that satisfies Equation (1).

$\begin{matrix}{{\frac{t \cdot E \cdot 1000}{2{{\sigma_{s} - \sigma_{m}}}} \times 0.5} \leq R \leq {\frac{t \cdot E \cdot 1000}{2{{\sigma_{s} - \sigma_{m}}}} \times 4}} & (1)\end{matrix}$

wherein each parameter in Equation (1) is as follows:t is a plate thickness (mm) of the blank;σ_(s) is a short direction bend outer surface stress (MPa) of the blankto form the top plate in the short direction;σ_(m) is an average stress in cross section of short direction (MPa) ofthe portion of the blank to form the top plate; andE is a Young's Modulus (GPa) of sheet steel configuring the blank.

A manufacturing method for a pressed component of a third aspectaccording to the present disclosure is a manufacturing method for aspecific pressed component, wherein a die and a punch are employed tobend a blank from the punch side toward the die side in a state in whichthe punch is caused to contact a first portion of the blank where thetwo end ridge line portions are to be formed, and to sandwich a secondportion of the blank where the top plate is to be formed between the dieand the punch and to indent the second portion from the die side towardthe punch side such that the second portion has a radius of curvature R(mm) that satisfies Equation (2)

$\begin{matrix}{\frac{t \cdot E \cdot 1000}{2 \cdot \sigma_{TS}} \leq R \leq \frac{t \cdot E \cdot 1000}{\sigma_{YP}}} & (2)\end{matrix}$

wherein each parameter in Equation (2) is as follows:t is a plate thickness (mm) of the blank;σ_(TS) is a tensile strength (MPa) of the blank;σ_(YP) is a yield stress (MPa) of the blank; andE is a Young's Modulus (GPa) of sheet steel configuring the blank.

A manufacturing method for a pressed component of a fourth aspectaccording to the present disclosure is the manufacturing method for aspecific pressed component of the first to the third aspect, wherein anapex face of the punch is curved as viewed along a direction in whichthe punch and the die face each other, and a groove that is curved so asto follow the apex face of the punch is formed in the die, and a pressedcomponent is manufactured in which the top plate is curved as viewedalong a plate thickness direction of the top plate.

A manufacturing method for a pressed component of a fifth aspectaccording to the present disclosure is the manufacturing method for aspecific pressed component of the first to the fourth aspect, wherein anapex face of the punch is curved in a convex profile bowing toward thedie side as viewed along an orthogonal direction orthogonal to both adirection in which the punch and the die face each other and the lengthdirection of the punch, and a groove that is curved so as to follow theapex face of the punch is formed in the die, and a pressed component ismanufactured in which the top plate is curved as viewed along a shortdirection of the top plate.

A pressed component according to the present disclosure is a specificpressed component, in which the top plate includes a minimum portionwhere the Vickers hardness value is a minimum value between one end andanother end in a short direction of the top plate, and maximum portionswhere the Vickers hardness value is a maximum value in each range out ofa first range between the minimum portion and the one end, and a secondrange between the minimum portion and the other end.

A mold according to the present disclosure is a mold for manufacturing apressed component configured including an elongated top plate, ridgeline portions at both short direction ends of the top plate, andvertical walls that face each other in a state extending from the ridgeline portions. The mold includes a punch and die. An apex face of thepunch is a recessed face having a radius of curvature R (mm) of from 38mm to 725 mm, and a blank is pressed between the punch and the die bysandwiching a portion of the blank where the top plate is to be formedbetween the die and the punch and indenting the portion of the blankfrom the die side toward the punch side.

A press apparatus according to the present disclosure includes the moldaccording to the present disclosure, as described above, and a movingsection that moves the punch relative to the die.

Advantageous Effects of Invention

A specific pressed component in which closing in of the vertical wallsdue to spring-back is suppressed can be manufactured by employing themanufacturing method for a pressed component according to the presentdisclosure.

In the pressed component according to the present disclosure, the amountby which the vertical walls close in due to spring-back is small.

A specific pressed component in which closing in of the vertical wallsdue to spring-back is suppressed can be manufactured by employing themold according to the present disclosure.

A specific pressed component in which closing in of the vertical wallsdue to spring-back is suppressed can be manufactured by employing thepress device according to the present disclosure.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a top view illustrating a roof member (pressed component) ofa first exemplary embodiment.

FIG. 1B is a side view illustrating a roof member of the first exemplaryembodiment.

FIG. 1C is a cross-section taken along 1C-1C in FIG. 1A.

FIG. 1D is a cross-section taken along 1D-1D in FIG. 1A.

FIG. 2A is a perspective view of a mold of a first press device employedin a first pressing process of a manufacturing method of a roof memberof the first exemplary embodiment.

FIG. 2B is a vertical cross-section of a first press device employed ina first pressing process of a manufacturing method of a roof member ofthe first exemplary embodiment.

FIG. 3A is a perspective view of a mold of a second press deviceemployed in a second pressing process of a manufacturing method of aroof member of the first exemplary embodiment.

FIG. 3B is a vertical cross-section of a second press device employed ina second pressing process of a manufacturing method of a roof member ofthe first exemplary embodiment.

FIG. 4A is a cross-section of an intermediate formed component formed bya first pressing process of the first exemplary embodiment, taken along1C-1C in FIG. 1A.

FIG. 4B is a cross-section of an intermediate formed component formed bya first pressing process of the first exemplary embodiment, taken along1D-1D in FIG. 1A.

FIG. 4C is a cross-section of a roof member manufactured by undergoing asecond pressing process of the first exemplary embodiment, taken along1C-1C in FIG. 1A.

FIG. 4D is a cross-section of an intermediate formed component formed byundergoing a second pressing process of the first exemplary embodiment,taken along 1D-1D in FIG. 1A.

FIG. 5A is a cross-section of an intermediate formed component formed bya first pressing process of the first exemplary embodiment, andillustrates the cross-section taken along 1C-1C in FIG. 1A in detail.

FIG. 5B is a cross-section of an intermediate formed component formed bya first pressing process of the first exemplary embodiment, andillustrates the cross-section taken along 1D-1D in FIG. 1A in detail.

FIG. 5C is a cross-section of a roof member manufactured by undergoing asecond pressing process of the first exemplary embodiment, andillustrates the cross-section taken along 1C-1C in FIG. 1A in detail.

FIG. 5D is a cross-section of a roof member manufactured by undergoing asecond pressing process of the first exemplary embodiment, andillustrates the cross-section taken along 1D-1D in FIG. 1A in detail.

FIG. 6A is a cross-section of a length direction central portion of anintermediate formed component formed by a first pressing process of thefirst exemplary embodiment.

FIG. 6B is a cross-section of a portion of an intermediate formedcomponent formed by a first pressing process of the first exemplaryembodiment that corresponds to a cross-section taken along 1C-1C in FIG.1A.

FIG. 6C is a cross-section of a length direction central portion of aroof member manufactured by undergoing a second pressing process of thefirst exemplary embodiment.

FIG. 6D is a cross-section of a roof member manufactured by undergoing asecond pressing process of the first exemplary embodiment, taken along1C-1C in FIG. 1A.

FIG. 7A is a cross-section taken along 1C-1C in FIG. 1A of anintermediate formed component formed by a first pressing process of thefirst exemplary embodiment, and is a cross-section that illustratesangles formed between vertical walls and flanges in detail.

FIG. 7B is a cross-section taken along 1D-1D in FIG. 1A of anintermediate formed component formed by a first pressing process of thefirst exemplary embodiment, and is a cross-section that illustratesangles formed between vertical walls and flanges in detail.

FIG. 7C is a cross-section taken along 1C-1C in FIG. 1A of a roof membermanufactured by undergoing a second pressing process of the firstexemplary embodiment, and is a cross-section that illustrates anglesformed between vertical walls and flanges in detail.

FIG. 7D is a cross-section taken along 1D-1D in FIG. 1A of a roof membermanufactured by undergoing a second pressing process of the firstexemplary embodiment, and is a cross-section that illustrates anglesformed between vertical walls and flanges in detail.

FIG. 8A is a top view illustrating a roof member of a second exemplaryembodiment.

FIG. 8B is a side view illustrating a roof member of the secondexemplary embodiment.

FIG. 8C is a cross-section taken along 8C-8C in FIG. 8A.

FIG. 8D is a cross-section taken along 8D-8D in FIG. 8A.

FIG. 9 is a vertical cross-section of a first press device employed in afirst pressing process of a manufacturing method of a roof member of thesecond exemplary embodiment.

FIG. 10 is a vertical cross-section of a second press device employed ina second pressing process of a manufacturing method of a roof member ofthe second exemplary embodiment.

FIG. 11A is a top view illustrating a roof member of a third exemplaryembodiment.

FIG. 11B is a side view illustrating a roof member of the thirdexemplary embodiment.

FIG. 11C is a cross-section taken along 11C-11C in FIG. 11A.

FIG. 11D is a cross-section taken along 11D-11D in FIG. 11A.

FIG. 12 is a diagram for explaining an evaluation method for twistingand bending.

FIG. 13 is a graph illustrating results from measuring twisting andbending in a top plate of a roof member 1 (Example 1) manufactured by aroof member manufacturing method of the first exemplary embodiment, anda roof member (Comparative Example 1) manufactured by a roof membermanufacturing method of a second comparative embodiment.

FIG. 14 is a graph illustrating results from measuring the Vickershardness of a top plate as measured in a range spanning from one shortdirection end to another short direction end of a top plate of Example1, and the Vickers hardness of a top plate as measured in a rangespanning from one short direction end to another short direction end ofa top plate of Comparative Example 1.

FIG. 15 is a table illustrating evaluation results based on simulationregarding twisting in top plates of roof members of respective Examples(Examples 2 to 8) of the first exemplary embodiment, and twisting in topplates of roof members of respective Comparative Examples (ComparativeExamples 2 to 6) of the second comparative embodiment.

FIG. 16 is a table illustrating evaluation results based on simulationregarding twisting in top plates of roof members of respective Examples(Examples 9 to 14) of the second exemplary embodiment, and twisting intop plates of roof members of respective Comparative Examples(Comparative Examples 7 to 11) of the second comparative embodiment.

DESCRIPTION OF EMBODIMENTS Summary

Explanation follows regarding the three exemplary embodiments (a first,a second, and a third exemplary embodiment) as embodiments forimplementing the present disclosure. This will be followed byexplanation regarding Examples. Note that in the present specification,exemplary embodiments refer to embodiments for implementing the presentdisclosure.

First Exemplary Embodiment

Explanation follows regarding the first exemplary embodiment. First,explanation follows regarding configuration of a roof member (see FIG.1A, FIG. 1B, FIG. 1C, and FIG. 1D) of the present exemplary embodiment.Next, explanation is given regarding configuration of a press apparatus17 (see FIG. 2A, FIG. 2B, FIG. 3A, and FIG. 3B) of the present exemplaryembodiment. This will be followed by explanation regarding amanufacturing method of the roof member of the present exemplaryembodiment. This will then be followed by explanation regardingadvantageous effects of the present exemplary embodiment.

Roof Member Configuration

First, explanation follows regarding configuration of the roof member 1of the present exemplary embodiment, with reference to the drawings.Note that the roof member 1 is an example of a pressed component and aspecific pressed component.

As illustrated in FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D, the roofmember 1 is an elongated member and has a substantially hat-shapedcross-section profile integrally configured including a top plate 2, twoconvex ridge line portions 3 a, 3 b, two vertical walls 4 a, 4 b, twoconcave ridge line portions 5 a, 5 b, and two flanges 6 a, 6 b. Notethat the convex ridge line portions 3 a, 3 b are an example of ridgeline portions. The roof member 1 is, for example, configured by acomponent cold pressed from a high tensile steel stock sheet having 1310MPa grade tensile strength. Namely, the roof member 1 of the presentexemplary embodiment is, for example, configured by a component coldpressed from a high tensile steel stock sheet having a tensile strengthof from 440 MPa to 1600 MPa.

As illustrated in FIG. 1A and FIG. 1B, the top plate 2 is elongated. Asillustrated in FIG. 1A, the top plate 2 is curved along its lengthdirection when viewed from the upper side of the top plate 2, namely,curved along arrow L1 in the drawings. As illustrated in FIG. 1B, thetop plate 2 is also curved along its length direction when viewed fromthe side of a side-face of the top plate 2, namely, curved along arrowL2 in the drawings. Namely, in side view, the roof member 1 is curvedalong its length direction such that the top plate 2 is curved in aconvex profile bowing toward the top plate 2 side.

As illustrated in FIG. 1A and FIG. 1B, the two convex ridge lineportions 3 a, 3 b are formed at both short direction ends of the topplate 2. The two vertical walls 4 a, 4 b face each other in a stateextending from the respective convex ridge line portions 3 a, 3 b.Namely, the roof member 1 of the present exemplary embodiment isconfigured including the elongated top plate 2, the convex ridge lineportions 3 a, 3 b at both short direction ends of the top plate 2, andthe vertical walls 4 a, 4 b opposing each other in a state extendingfrom the respective convex ridge line portions 3 a, 3 b.

In the present exemplary embodiment, for example, respectivecross-sections taken perpendicularly to the length direction of the topplate 2 extend in a straight-line shape along the short direction ateach length direction position. Namely, when the top plate 2 of thepresent exemplary embodiment is viewed in respective perpendicularcross-sections along the length direction, as illustrated in FIG. 1C andFIG. 1D, the top plate 2 is flat at each length direction position. Notethat as illustrated in FIG. 1D, the convex ridge line portion 3 a is aportion that connects the top plate 2 and the vertical wall 4 atogether, and is a curved portion when viewed in respectivecross-sections taken perpendicularly to the length direction of the topplate 2. The two single-dotted dashed lines in the drawings respectivelyindicate the two ends of the convex ridge line portion 3 a connected tothe top plate 2 and the vertical wall 4 a. Illustration of both ends ofthe convex ridge line portion 3 b by single-dotted dashed lines isomitted from the drawings; however, the convex ridge line portion 3 b isa portion that connects the top plate 2 and the vertical wall 4 btogether, and is a curved portion when viewed in respectivecross-sections taken perpendicularly to the length direction of the topplate 2. As illustrated in FIG. 14, the top plate 2 of the presentexemplary embodiment includes a central portion at the short directioncenter of the top plate 2 where the Vickers hardness value of the topplate 2 is a minimum value, and maximum portions where the respectiveVickers hardness value of the top plate 2 is a maximum value, namely, ata maximum value in each range out of a first range that is the rangebetween the central portion and one short direction end of the top plate2 and a second range that is the range between the center portion andanother short direction end of the top plate 2. Note that in the presentspecification, the central portion at the short direction center of thetop plate 2 where the Vickers hardness value is the minimum value iscalled the minimum portion.

The roof member 1 of the present exemplary embodiment is a membermanufactured by pressing a blank BL, illustrated in FIG. 2B, using amanufacturing method of the roof member 1 of the present exemplaryembodiment, described later. Note that the Vickers hardness of the blankBL is, for example, 430 HV. By contrast, the Vickers hardness of theminimum portion of the top plate 2 of the roof member 1 is, for example,approximately 417 HV, as illustrated in FIG. 14. Namely, the Vickershardness of the central portion of the top plate 2 is less than theVickers hardness of the blank BL prior to being pressed. Further, theVickers hardness of an end portion of the flange 6 b of the roof member1 is, for example, 430 HV. Namely, the Vickers hardness of the centralportion of the top plate 2 is less than the Vickers hardness of the endportion of the flange 6 b. In other words, it may be said that in theroof member 1 of the present exemplary embodiment, the top plate 2 issofter than the end portion of the flange 6 b. The end portion of theflange 6 b refers to a portion of the flange 6 b of the roof member 1from an end on the opposite side to the side connected to the concaveridge line portion 5 b to up to 5 mm toward the ridge line portion 5 bside. Note that as explained above, the reason the end portion of theflange 6 b is harder than the top plate 2 is thought to be because theflange 6 b is not deformed as much as the top plate 2 in themanufacturing method of the roof member 1, described later.

Further, the two concave ridge line portions 5 a, 5 b are respectivelyformed at end portions of the two vertical walls 4 a, 4 b on theopposite side to the side connected to the top plate 2. The two flanges6 a, 6 b are connected to the two respective concave ridge line portions5 a, 5 b. Illustration of the concave ridge line portion 5 a is omittedfrom the drawings; however, the concave ridge line portion 5 a is aportion that connects the vertical wall 4 a and the flange 6 a together,and is a curved portion when viewed in respective cross-sections takenperpendicularly to the length direction of the top plate 2. Illustrationof the two ends of the concave ridge line portion 5 b by single-dotteddashed lines is omitted from the drawings; however, the concave ridgeline portion 5 b is a portion that connects the vertical wall 4 b andthe flange 6 b together, and is a curved portion when viewed inrespective cross-sections taken perpendicularly to the length directionof the top plate 2.

As illustrated in FIG. 1A, as viewed from the top plate 2 side in astate in which the top plate 2 is disposed so as to be orientated at aposition on the upper side, the roof member 1 is curved from a front endportion 1 a, namely one length direction end portion, to a rear endportion 1 b, namely another length direction end portion. From anotherperspective, as illustrated in FIG. 1A and FIG. 1B, it may be said thatthe roof member 1 is integrally configured including a first section 8including the front end portion 1 a, a third section 10 including therear end portion 1 b, and a second section 9 connecting the firstsection 8 and the third section 10 together.

Note that in the present exemplary embodiment, in top view (as viewedfrom the upper side of the top plate 2) the radius of curvature R of thefirst section 8 is, for example, set to from 2000 mm to 9000 mm, theradius of curvature R of the second section 9 is, for example, set tofrom 500 mm to 2000 mm, and the radius of curvature R of the thirdsection 10 is, for example, set to from 2500 mm to 9000 mm. Moreover, asillustrated in FIG. 1B, in the present exemplary embodiment, in sideview (as viewed from a width direction side of the top plate 2) theradius of curvature R of the first section 8 is, for example, set tofrom 3000 mm to 15000 mm, the radius of curvature R of the secondsection 9 is, for example, set to from 1000 mm to 15000 mm, and theradius of curvature R of the third section 10 is, for example, set tofrom 3000 mm to 15000 mm. As described above, the radius of curvature Rof the first section 8 and the radius of curvature R of the thirdsection 10 are each larger than the radius of curvature R of the secondsection 9.

As illustrated in FIG. 1D, a height from a plate thickness center at theend of curvature at a curvature start point on the top plate 2 side ofthe convex ridge line portion 3 a, namely, from a plate thickness centerof the top plate 2, up to an end of the vertical wall 4 a on the concaveridge line portion 5 a side, is a height h. In this configuration, astep 11 a having a step amount a2 (mm) is formed on the vertical wall 4a, so as to span the length direction of the vertical wall 4 a at aportion thereof that is a distance of not less than 40% of the height haway from the plate thickness center of the top plate 2. Further, asillustrated in FIG. 1D, a height from a plate thickness center of theend of curvature at a curvature start point on the top plate 2 side ofthe convex ridge line portion 3 b, namely, from a plate thickness centerof the top plate 2, up to an end of the vertical wall 4 b on the concaveridge line portion 5 b side, is a height h′. In this configuration, astep 11 a′ having a step amount a2′ (mm) is formed on the vertical wall4 b, so as to span the length direction of the vertical wall 4 b at aportion thereof that is a distance of not less than 40% of the height haway from the plate thickness center of the top plate 2.

As illustrated in FIG. 1C and FIG. 1D, the cross-section profiles of theflanges 6 a, 6 b differ between the front end portion 1 a and the rearend portion 1 b in the length direction of the roof member 1.Specifically, the angle of the flange 6 b with respect to the verticalwall 4 b is 30° at the front end portion 1 a and 40° at the rear endportion 1 b. Further, the respective angles of the flanges 6 a, 6 b withrespect to the vertical wall 4 a change progressively along the lengthdirection. Further, the width of the short direction of the top plate 2changes along the length direction so as become progressively wider fromthe front end portion 1 a to the rear end portion 1 b. Note that asillustrated in FIG. 1A to FIG. 1D, the angle formed between the verticalwall 4 b and the flange 6 b at the first section 8 is preferably no lessthan the angle formed between the vertical wall 4 b and the flange 6 bat the third section 10.

The foregoing explanation relates to configuration of the roof member 1of the present exemplary embodiment.

Press Apparatus Configuration

Next, explanation follows regarding the press apparatus 17 of thepresent exemplary embodiment, with reference to the drawings. The pressapparatus 17 of the present exemplary embodiment is used to manufacturethe roof member 1 of the present exemplary embodiment. As illustrated inFIG. 2A, FIG. 2B, FIG. 3A, and FIG. 3B, the press apparatus 17 isconfigured including a first press device 18 and a second press device19. The press apparatus 17 of the present exemplary embodiment employsthe first press device 18 to draw the blank BL illustrated in FIG. 2B soas to press the blank BL to form an intermediate formed component 30,illustrated in FIG. 3B, and then uses the second press device 19 topress the intermediate formed component 30 to manufacture a manufacturedcomponent, namely the roof member 1. Note that the blank BL isconfigured by elongated high tensile sheet steel as a base material formanufacturing the roof member 1.

Note that as illustrated in FIG. 3B, the intermediate formed component30 is a substantially hat-shaped member configured including the topplate 2, two convex ridge line portions 32 a, 32 b, two vertical walls33 a, 33 b, two concave ridge line portions 34 a, 34 b, and two flanges35 a, 35 b. Moreover, in the present specification, “pressing” refers toa process of setting a forming target in a mold, closing the mold, andthen opening the mold. Note that in the present exemplary embodiment,the blank BL and the intermediate formed component 30 are examples offorming targets. Further, a first mold 20 and a second mold 40,described later, are examples of molds.

First Press Device

The first press device 18 is configured including the first mold 20 anda first moving device 25. As illustrated in FIG. 2B, the first mold 20includes an upper mold 21, a lower mold 22, a first holder 23, and asecond holder 24. The upper mold 21 is disposed at the upper side, andthe lower mold 22 is disposed at the lower side. The first press device18 is an example of a press device. The first mold 20 is an example of amold. The upper mold 21 is an example of a die. The lower mold 22 is anexample of a punch. When forming the blank BL into the intermediateformed component 30, the first press device 18 has a function of, in astate in which the blank BL is in contact with the lower mold 22 atportions of the blank where the two convex ridge line portions 3 a, 3 bare to be formed, employing the upper mold 21 and the lower mold 22 tobend the blank BL into a profile protruding from the lower mold 22 sidetoward the upper mold 21 side, before sandwiching the portion of theblank BL where the top plate 2 is to be formed between the upper mold 21and the lower mold 22 and indenting the portion of the blank BL wherethe top plate 2 is to be formed from the upper mold 21 side toward thelower mold 22 side, such that the portion of the blank BL where the topplate 2 is to be formed has a radius of curvature R (mm) that satisfiesthe following Equation (1). The portions of the blank BL where the twoconvex ridge line portions 3 a, 3 b are to be formed are an example of afirst portion. Further, the portion of the blank BL where the top plate2 is to be formed is an example of a second portion.

$\begin{matrix}{{\frac{t \cdot E \cdot 1000}{2{{\sigma_{s} - \sigma_{m}}}} \times 0.5} \leq R \leq {\frac{t \cdot E \cdot 1000}{2{{\sigma_{s} - \sigma_{m}}}} \times 4}} & (1)\end{matrix}$

Each parameter in Equation (1) is as follows.t is a plate thickness (mm) of the blank BL;σ_(s) is a short direction bend outer surface stress (MPa) of theportion of the blank BL to form the top plate;σ_(m) is an average stress in cross section of short direction (MPa) ofthe portion of the blank BL to form the top plate; andE is a Young's Modulus (GPa) of sheet steel configuring the blank BL.

Note that the first press device 18 is configured so as to sandwich thesecond portion between the upper mold 21 and the lower mold 22 and toindent the second portion from the upper mold 21 side toward the lowermold 22 side such that a portion of the second portion contacting thelower mold 22 satisfies the radius of curvature R (mm) in Equation (1).

Further, of the parameters in Equation (1), σ_(s) and σ_(m) are found byperforming forming analysis of conditions to achieve a flat top plate 2.

For a high tensile sheet steel blank having 980 MPa grade tensilestrength, the radius of curvature R (mm) in Equation (1) is from 38 mmto 1300 mm. Moreover, for a high tensile sheet steel blank having 1310MPa grade tensile strength, the radius of curvature R (mm) in Equation(1) is from 32 mm to 1020 mm. Moreover, for a high tensile sheet steelblank having 1470 MPa grade tensile strength, the radius of curvature R(mm) in Equation (1) is from 30 mm to 725 mm. Accordingly, whensandwiching the portion of the blank BL that will form the top plate 2between the upper mold 21 and the lower mold 22 and indenting thisportion from the upper mold 21 side toward the lower mold 22 side suchthat the radius of curvature R (mm) of the portion of the blank BL thatwill form the top plate 2 is within a range of from 38 mm to 725 mm,pressing that satisfies Equation (1) is performed on a high tensilesheet steel blank having at least a strength within a range of from 980MPa grade to 1470 MPa grade. As described above, it may be said thatwhen the blank BL is formed into the intermediate formed component 30,the first press device 18 has a function to sandwich the portion of theblank BL that will form the top plate 2 between the upper mold 21 andthe lower mold 2 and to indent the portion of the blank BL that willform the top plate 2 from the upper mold 21 side toward the lower mold22 side such that the radius of curvature R (mm) of the portion of theblank BL that will form the top plate 2 is within a range of from 38 mmto 725 mm.

As illustrated in FIG. 2A, the upper mold 21 and the lower mold 22 areeach elongated. An apex face of the lower mold 22 projects out and iscurved along the length direction when the upper mold 21 and the lowermold 22 are viewed along the direction in which the upper mold 21 andthe lower mold 22 face each other, and a groove that curves so as tofollow the apex face of the lower mold 22 is formed in the upper mold21, as illustrated in FIG. 2A and FIG. 2B. Further, when the upper mold21 and the lower mold 22 are viewed along the short direction of theupper mold 21 and the lower mold 22, this being a direction orthogonalto the direction in which the upper mold 21 and the lower mold 22 faceeach other, the apex face of the lower mold 22 is curved in a convexprofile bowing toward the upper mold 21 side, and the groove that curvesfollowing the apex face of the lower mold 22 is formed in the upper mold21, as illustrated in FIG. 2A and FIG. 2B. An apex face 22 c of thelower mold 22 is configured by a recessed face having a radius ofcurvature R (mm) of from 38 mm to 725 mm. Moreover, as viewed along thelength direction, the groove-bottom of the groove of the upper mold 21projects out with a radius of curvature R (mm) toward the lower mold 22side, and a portion of the lower mold 22 opposing the bottom of thegroove of the upper mold 21 (apex face) is recessed toward the uppermold 21 side with a radius of curvature R (mm) (see FIG. 2B). The radiusof curvature R (mm) of the present exemplary embodiment is, for example,100 mm.

Note that as illustrated in FIG. 2A and FIG. 2B, the two short directionends of the apex face 22 c of the lower mold 22 are referred to asshoulders 22 d. When the first press device 18 forms the blank BL intothe intermediate formed component 30, each shoulder 22 d corresponds toa portion of the lower mold 22 contacting the second portion of theblank BL.

Further, when the lower mold 22 is viewed along the length direction,step portions 22 a, 22 a′ are respectively formed at the two side facesof the lower mold 22, as illustrated in FIG. 2B. Further, step portions21 a, 21 a′ that follow the step portions 22 a, 22 a′ are respectivelyformed to the two side faces of the groove in the upper mold 21.

The first holder 23 and the second holder 24 are elongated following theupper mold 21 and the lower mold 22. As illustrated in FIG. 2B, thefirst holder 23 and the second holder 24 are respectively disposed atthe two short direction sides of the lower mold 22. Further, the firstholder 23 and the second holder 24 are biased toward the upper side bysprings 26, 27.

The first moving device 25 is configured so as to move the upper mold 21toward the lower mold 22. Namely, the first moving device 25 isconfigured so as to move the upper mold 21 relative to the lower mold22. When the first moving device moves the upper mold 21 toward thelower mold 22 in a state in which the blank BL is disposed at apredetermined position in a gap between the upper mold 21 and the lowermold 22, as illustrated in FIG. 2B, the blank BL is pressed so as toform the intermediate formed component 30 in a state in which both shortdirection end sides of the blank BL are sandwiched between therespective first holder 23 and the second holder 24, and the upper mold21.

In the above explanation, the first press device 18 is configured tocurve the second portion of the blank BL in a convex profile bowing fromthe upper mold 21 side toward the lower mold 22 side such that thesecond portion has a radius of curvature R mm that satisfies Equation(1). However, the first press device 18 may curve the second portion ofthe blank BL in a convex profile bowing from the upper mold 21 sidetoward the lower mold 22 side such that the second portion has a radiusof curvature R (mm) that satisfies Equation (2) instead of Equation (1).

$\begin{matrix}{\frac{t \cdot E \cdot 1000}{2 \cdot \sigma_{TS}} \leq R \leq \frac{t \cdot E \cdot 1000}{\sigma_{YP}}} & (2)\end{matrix}$

Note that each parameter in Equation (2) is as follows:t is a plate thickness (mm) of the blank;σ_(TS) is a tensile strength (MPa) of the blank;σ_(YP) is a yield stress (MPa) of the blank; andE is a Young's Modulus (GPa) of sheet steel configuring the blank.σ_(TS) is, for example, a shipment test value from the mill sheetlisting obtained based on Tensile Testing for a JIS No. 5 sample.Further, σYP is, for example, a shipment test value from the mill sheetlisting obtained based on Tensile Testing for a JIS No. 5 sample.

The inventors of the present application have made investigationpertaining to numerical value analysis of stress generated at the outersurface, namely an upper face, and at the inner surface, namely a backface, of the top plate 2 when forming the roof member 1 and roof members1A, 1B, described later, with the plate thickness and material strengthof the blank BL, the shape of the top plate 2, the pressing method, suchas bending or drawing, and so on serving as the parameters. It wasdiscovered from the results that when the roof members 1, 1A, and 1B arepressed without using a pad, deviatoric stress σ that contributes towarping of the top plate 2 changes depending on the material strength ofthe blank BL and satisfies the following condition A.

0.5 σ_(YP)≤σ≤σ_(TS)  Condition A:

Further, based on the assumption that deformation of the top plate 2during pressing is elastic deformation, relationship B between theradius of curvature R (mm), the deviatoric stress σ (MPa), the platethickness (mm) of the blank BL, and the Young's Modulus (GPa) of thesheet steel configuring the blank BL satisfy the following relationship.

α=E×1000×t/2R  Relationship B:

Equation (2) is derived from condition A and relationship B above.

Note that of the parameters in Equation (2), σ_(TS) and σ_(YP) are foundby performing forming analysis under the condition of forming a flat topplate 2.

Second Press Device

The second press device 19 is configured including the second mold 40and a second moving device 45. As illustrated in FIG. 3B, the secondmold 40 includes an upper mold 41, a lower mold 43, and a holder 42. Theupper mold 41 is disposed at the upper side, and the lower mold 43 isdisposed at the lower side. In the second press device 19, in a state inwhich the intermediate formed component 30 has been fitted onto thelower mold 43, the upper mold 41 is moved toward the lower mold 43 sideby the second moving device so as to change the angles of the twoflanges 35 a, 35 b of the intermediate formed component 30.

Further, when viewing the lower mold 43 along the short direction, stepportions 43 a are respectively formed at the two side faces of the lowermold 43, as illustrated in FIG. 3B. Further, step portions 41 afollowing the respective step portions 43 a are formed at the two sidefaces of the groove of the upper mold 41.

The foregoing was an explanation relating to configuration of the pressapparatus 17 of the present exemplary embodiment.

Roof Member Manufacturing Method

Explanation follows regarding a manufacturing method of the roof member1 of the present exemplary embodiment, with reference to the drawings.The manufacturing method of the roof member 1 of the present exemplaryembodiment is performed using the press apparatus 17. Further, themanufacturing method of the roof member 1 of the present exemplaryembodiment includes a first pressing process, this being a processperformed by the first press device 18, and a second pressing process,this being a process performed by the second press device 19.

First Pressing Process

In the first pressing process, the blank BL is disposed at thepredetermined position in the gap between the upper mold 21 and thelower mold 22, namely, the blank BL is set in the mold 20 at apredetermined position. Next, an operator operates the first pressdevice 18 such that the upper mold 21 is moved toward the lower mold 22side by the first moving device 25, and the blank BL is drawn so as topress the blank BL. When this is performed, first, in a state in whichthe first portion of the blank BL is in contact with the shoulders 22 dof the lower mold 22, the first press device 18 bends the blank BL intoa profile protruding from the lower mold 22 side toward the upper mold21 side, as illustrated in FIG. 2B. Next, the first press device 18sandwiches the second portion of the blank BL between the upper mold 21and the lower mold 22 and indents the second portion from the upper mold21 side toward the lower mold 22 side. Namely, in the first pressingprocess, the upper mold 21 and the lower mold 22 are used to press theblank BL. The intermediate formed component 30 is formed from the blankBL as a result.

Note that the mold 20 employed in the first pressing process ismanufactured according to the parameters of the blank BL so as tosatisfy the conditions of Equation (1) or Equation (2). For example, thefirst pressing process is performed using an upper mold 21 and lowermold 22, namely the mold 20, manufactured according to the platethickness t of the blank BL and the Young's modulus E of the sheet steelconfiguring the blank BL so as to satisfy Equation (1) or Equation (2).Further, for example, plural molds 40 having different shapes to eachother are prepared, and the first pressing process is performed afterselecting the mold 20 according to the plate thickness t of the blank BLand the Young's Modulus E of the sheet steel configuring the blank BL soas to satisfy Equation (1) or Equation (2), and attaching the selectedmold 20 to the body of the first press device 18.

Further, in the first pressing process, as illustrated in FIG. 5A, FIG.5B, FIG. 6A, and FIG. 6B, steps 36 a, 36 a′ having a step amount a1 (mm)as defined by the following Equation (3) and Equation (4) arerespectively formed on the two vertical walls 33 a, 33 b of theintermediate formed component 30, at portions thereof at a distance ofnot less than 40% of the height h, h′ away from the top plate 2.

a1≥a2  (3)

a1≤0.2W  (4)

Note that the reference sign a1 indicates the step amount (mm) of theintermediate formed component 30, the reference sign a2 indicates thestep amount (mm) of the roof member 1, and the reference sign Windicates the short direction width (mm) of the top plate 2 of the roofmember 1.

Further, in the first pressing process, as illustrated in FIG. 7A andFIG. 7B, the vertical wall 33 a and the flange 35 a are formed such thatan angle DI1 formed between the vertical wall 33 a and the flange 35 aof the intermediate formed component 30 satisfies the following Equation(5).

1.0×DI2≤DI1≤1.2×DI2  (5)

The reference sign DI1 indicates the angle formed between the verticalwall 33 a and the flange 35 a of the intermediate formed component 30,and the reference sign DI2 indicates the angle formed between thevertical wall 4 a and the flange 6 a of the roof member 1.

Further, in the first pressing process, the vertical wall 33 b and theflange 35 b of the intermediate formed component 30 are formed so as tosatisfy the following Equation (6).

0.9≤DOF1/DOR1≤1  (6)

Note that DOF1 is the angle formed between the flange 35 b and thevertical wall 33 b including one end portion of the intermediate formedcomponent 30, and DOR1 is the angle formed between the flange 35 b andthe vertical wall 33 b including another end portion of the intermediateformed component 30.

Further, in the first pressing process, an end of the material of theblank BL flows in and the blank BL is flexed so as to form the flange 35b at the outside of the intermediate formed component 30.

The intermediate formed component 30 is then removed from the first mold20, thereby completing the first pressing process.

Note that as described above, when the intermediate formed component 30is formed by the first press device 18, the second portion of the blankBL is indented from the upper mold 21 side toward the lower mold 22 sidesuch that the radius of curvature R (mm) of the second portion satisfiesEquation (1) or Equation (2). When the first mold 20 is opened, asillustrated in FIG. 4A and FIG. 4B, the cross-section of theintermediate formed component 30 in the length direction of the topplate 2 adopts a deformed state that is flatter than when the mold wasclosed, namely, a state in which the radius of curvature has becomelarger.

Second Pressing Process

Next, the intermediate formed component 30 is fitted onto the lower mold43 of the second mold 40 of the second press device 19. Then, when anoperator operates the second press device 19, the upper mold 41 is movedtoward the lower mold 43 side by the second moving device, and theangles of the two flanges 35 a, 35B of the intermediate formed component30 are changed. The roof member 1 is thus manufactured from theintermediate formed component 30. Note that in the second pressingprocess, the intermediate formed component 30 is pressed such that thestep amounts of the vertical walls 33 a, 33 b of the intermediate formedcomponent 30 become a2. Further, in the second pressing process, asillustrated in FIG. 7A, FIG. 7B, FIG. 7C, and FIG. 7D, the intermediateformed component 30 is sandwiched between the upper mold 41 and thelower mold 43 and the intermediate formed component 30 is then pressedsuch that the vertical wall 33 a and the flange 35 a of the intermediateformed component 30 form the vertical wall 4 a and the flange 6 a of theroof member 1. Further, in the second pressing process, as illustratedin FIG. 7A, FIG. 7B, FIG. 7C, and FIG. 7D, the intermediate formedcomponent 30 is sandwiched between the upper mold 41 and the lower mold43, and between the upper mold 41 and the holder 42, and theintermediate formed component 30 is then pressed such that the verticalwall 33 b and the flange 35 b of the intermediate formed component 30form the vertical wall 4 b and the flange 6 b of the roof member 1.

The foregoing was an explanation relating to the manufacturing method ofthe roof member 1 of the present exemplary embodiment.

Advantageous Effects

Next, explanation follows regarding advantageous effects of the presentexemplary embodiment, with reference to the drawings.

Advantageous Effect of Causing Prior Contact of Lower Mold 22 againstFirst Portion of Blank BL

An advantageous effect of causing prior contact of the lower mold 22against the first portion of the blank BL (referred to below as firstportion prior contacting advantageous effect), is an advantageous effectin which, as illustrated in FIG. 2B, the blank BL is bent into a profileprotruding from the lower mold 22 side toward the upper mold 21 side ina state in which the shoulders 22 d of the lower mold 22 are caused tocontact the first portion of the blank BL, prior to then sandwiching theblank BL between the upper mold 21 and the lower mold 22 and indentingthe blank BL from the upper mold 21 side toward the lower mold 22 side.In other words, this is an advantageous effect to form the first portionof the blank BL before the second portion. Explanation follows regardingthe first portion prior contacting advantageous effect by comparing thepresent exemplary embodiment to a first comparative embodiment describedbelow. Note that in the first comparative embodiment, where componentsand the like employed in the present exemplary embodiment are alsoemployed, the same names and the like are used for such components, evenif they are not illustrated in the drawings.

In the case of the first comparative embodiment, the second portion ofthe blank BL is formed prior to the first portion. Thus, in the case ofthe first comparative embodiment, compressive stress arises in the topplate 2 during mold closure in the first pressing process as a result ofsurplus material that arises when indenting the blank BL. As a result,in the case of the first comparative embodiment, spring-back occurs inthe intermediate formed component 30 after the mold is opened in thefirst pressing process.

By contrast, in the case of the present exemplary embodiment, asillustrated in FIG. 2A, the blank BL is bent into a profile protrudingfrom the lower mold 22 side toward the upper mold 21 side in a state inwhich the shoulders 22 d of the lower mold 22 are caused to contact thefirst portion of the blank BL, prior to then sandwiching the blank BLbetween the upper mold 21 and the lower mold 22 and indenting the blankBL from the upper mold 21 side toward the lower mold 22 side. Namely, inthe case of the present exemplary embodiment, the first portion isformed before the second portion, thereby enabling a reduction insurplus material when indenting the blank BL compared to in the case ofthe first comparative embodiment. Accordingly, in the case of thepresent exemplary embodiment, compressive stress that arises in the topplate 2 during mold closure in the first pressing process can be reducedcompared to in the case of the first comparative embodiment.

The manufacturing method of the roof member 1 of the present exemplaryembodiment thereby enables the roof member 1 to be manufactured suchthat closing in of the vertical walls 4 a, 4 b due to spring-back issuppressed compared to in the first comparative embodiment.

Advantageous Effect of Performing First Pressing to Obtain Radius ofCurvature R Satisfying Equation (1)

An advantageous effect of performing the first pressing so as to obtaina radius of curvature R satisfying Equation (1) (referred to below asadvantageous effect of accordance to Equation (1)) is an advantageouseffect in which the second portion is indented from the upper mold 21side toward the lower mold 22 side in the first pressing process suchthat the portion of the blank BL that will form the top plate 2 attainsa radius of curvature R (mm) satisfying Equation (1), in other words,attains a radius of curvature satisfying Equation (2), or in yet otherwords, such that the radius of curvature R (mm) of the second portion ofthe blank BL is within a range of from 38 mm to 725 mm. Explanationfollows regarding the advantageous effect of accordance to Equation (1)by comparing the present exemplary embodiment to a second comparativeembodiment described below. Note that in the second comparativeembodiment, where components and the like employed in the presentexemplary embodiment are also employed, the same names and the like areused for such components, even if they are not illustrated in thedrawings.

In the case of the second comparative embodiment, the bottom of thegroove in the upper mold 21 of the first press device 18 is flat incross-section viewed along its length direction, and a portion of alower mold 22 opposing the bottom of the groove of the upper mold 21 isflat in cross-section viewed along its length direction. Further, in thecase of the second comparative embodiment, step portions 21 a are notformed to the upper mold 21, and step portions 22 a are not formed tothe lower mold 22. The second comparative embodiment is similar to thepresent exemplary embodiment with the exception of the points describedabove.

In the case of the second comparative embodiment, twisting occurs in thetop plate 2 due to residual deviatoric stress in the top plate 2 whenthe intermediate formed component 30 is formed in the first pressingprocess. As a result, a roof member 1 manufactured by a manufacturingmethod of the roof member 1 of the second comparative embodiment adoptsa twisted state, as indicated by Comparative Examples 2 to 6 in thetable in FIG. 15. This result is thought to be due to the vertical walls33 a, 33 b closing in due to spring-back after the first pressing,namely, after the mold is opened. Note that in the case of the secondcomparative embodiment, it is thought that the closing in of thevertical walls 33 a, 33 b due to spring-back after the first pressingoccurs via the following mechanism. Namely, in the first pressingprocess, the intermediate formed component 30 is formed by deforming thesecond portion of the blank BL into a profile protruding toward theupper side by the time that the mold is closed. Namely, in the gapbetween the upper mold 21 and the lower mold 22, the second portion ofthe blank BL is formed by being bent into a profile protruding towardthe upper side. Thus, the top plate 2 of the intermediate formedcomponent 30 of the second comparative embodiment is bent into a profileprotruding toward an outer surface side configuring the outer side incross-section view. As a result, stress attempting to cause the verticalwalls 33 a, 33 b to close in occurs in the top plate 2. Moreover, in thecase of the second comparative embodiment, the intermediate formedcomponent 30 is curved along its length direction, such that differencesin stress can occur between the two short direction end sides of the topplate 2, at respective positions perpendicular to the length directionof the top plate 2. As a result, the roof member 1 manufacturedaccording to the manufacturing method of the roof member 1 of the secondcomparative embodiment adopts a twisted state.

By contrast, in the case of the present exemplary embodiment, the secondportion is indented from the upper mold 21 side toward the lower mold 22side in the first pressing process such that the portion of the blank BLthat will form the top plate 2 attains a radius of curvature R (mm) thatsatisfies Equation (1), in other words, a radius of curvature thatsatisfies Equation (2), or in yet other words, such that the radius ofcurvature R (mm) of the second portion of the blank BL is within a rangeof from 38 mm to 725 mm. Thus, in the first pressing process of thepresent exemplary embodiment, the blank BL is deformed into a profileprotruding toward the upper side accompanying mold closure, and next,the portion of the blank BL that will form the top plate 2 is deformedto achieve a profile of the top plate 2 curving toward the lower sideduring mold closure. The mold is then opened, thereby forming theintermediate formed component 30. Namely, it is speculated that afterbeing plastically deformed toward the upper side, the top plate 2 of theintermediate formed component 30 of the present exemplary embodimentbears load from the upper side toward the lower side, thereby attaininga state in which the Bauschinger effect acts. As a result, twisting isless liable to arise in the top plate 2 of the intermediate formedcomponent 30 formed by the first pressing process of the presentexemplary embodiment than in the case of the second comparativeembodiment. This result is thought to be due to the fact that the amountby which the vertical walls 33 a, 33 b close in due to spring-back afterthe first pressing process is less than that in the case of the secondcomparative embodiment. Further, although the second pressing process isperformed after the first pressing process, the top plate 2 of theintermediate formed component 30 undergoes hardly any deformation in thesecond pressing process even when pressed. It is thought that as aresult there is no twisting or any twisting amount is small in the roofmember 1 manufactured according to the manufacturing method of the roofmember 1 of the present exemplary embodiment, compared to in the case ofthe second comparative embodiment, as illustrated by the graph in FIG.13, described later. Note that in the case of the present exemplaryembodiment, the top plate 2 of the intermediate formed component 30 hasa (substantially) flat shape in cross-section view along its lengthdirection due to forming the intermediate formed component 30 based onEquation (1) computed on the relationship between t, σ_(s), σ_(m), and Eserving as the parameters for the top plate 2, or based on Equation (2)computed on the relationship between t, σ_(TS), σ_(YP), and E serving asthe parameters for the top plate 2. This enables residual deviatoricstress to be suppressed from occurring at the press bottom dead centerin the second pressing process performed after the first pressingprocess. Further, in the case of the present exemplary embodiment, inthe first pressing process, the intermediate formed component 30 iscompleted only after the second portion of the blank BL has beenindented from the upper mold 21 side toward the lower mold 22 side.Accordingly, at respective positions perpendicular to the lengthdirection of the top plate 2, the convex ridge line portions 32 a, 32 bat the two short direction ends of the top plate 2 can be formed withangles that are more acute than in the case of the second comparativeembodiment. As a result, in the case of the present exemplaryembodiment, spring-back that attempts to open out the vertical walls 33a, 33 b is canceled out more easily than in the case of the secondcomparative embodiment. Accordingly, the roof member 1 in the presentexemplary embodiment is less liable to twist due to the intermediateformed component 30 curving along its length direction compared to theroof member 1 of the second comparative embodiment, regardless of thefact that differences arise between the stresses at the two shortdirection end sides of the top plate 2, at the respective positionsperpendicular to the length direction of the top plate 2.

Thus, the manufacturing method of the roof member 1 of the presentexemplary embodiment enables a roof member 1 to be manufactured thatsuppresses closing in of the vertical walls 4 a, 4 b due to spring-backmore effectively than in the second comparative embodiment, namely,compared to cases in which the portion of the blank BL that will formthe top plate 2 is pressed flat during mold closure in the firstpressing process. Thus, the manufacturing method of the roof member 1 ofthe present exemplary embodiment enables a roof member 1 to bemanufactured that suppresses twisting of the top plate 2 moreeffectively than in the second comparative embodiment, namely, comparedto cases in which the portion of the blank BL that will form the topplate 2 is pressed flat during mold closure in the first pressingprocess. Further, as illustrated by the graph in FIG. 13, twisting ofthe top plate 2 of a roof member 1 manufactured by the manufacturingmethod of the roof member 1 of the present exemplary embodiment issmaller than in a roof member 1 manufactured by the manufacturing methodof the roof member 1 of the second comparative embodiment. Further,using the first mold 20, the first press device 18, or the pressapparatus 17 of the present exemplary embodiment enables a roof member 1to be manufactured in which closing in of the vertical walls 4 a, 4 bdue to spring-back is more effectively suppressed than in the case ofthe second comparative embodiment. Thus, using the first mold 20, thefirst press device 18, or the press apparatus 17 of the presentexemplary embodiment enables a roof member 1 to be manufactured in whichtwisting of the top plate 2 is more effectively suppressed fromoccurring than in the case of the second comparative embodiment.

In particular, the present exemplary embodiment exhibits theadvantageous effect of being in accordance with Equation (1) in cases inwhich a blank BL configured by a high tensile sheet steel is pressed.Further, the advantageous effect of being accordance with Equation (1)is exhibited even in cases in which the top plate 2 is curved along itslength direction when viewing the top plate 2 from the upper side, as inthe case of the roof member 1 of the present exemplary embodiment.Moreover, the advantageous effect of being in accordance with Equation(1) is exhibited even in cases in which the roof member 1 is curved in aconvex profile bowing toward the top plate 2 side when viewing the topplate 2 along the short direction, as in the case of the roof member 1of the present exemplary embodiment.

Other Advantageous Effects

Explanation follows regarding other advantageous effects of the presentexemplary embodiment.

Advantageous Effect 1

In the case of the present exemplary embodiment, in the first pressingprocess, the steps 36 a, 36 a′ are formed to the vertical walls 33 a, 33b, and in the second pressing process, the step amount a1 of the steps36 a, 36 a′, namely the offset amount, is changed. Thus, the residualstress is reduced in each of the vertical walls 4 a, 4 b, such thatresidual deviatoric stress in the vertical walls 4 a, 4 b is alsoreduced. As a result, residual stress is reduced in upper portions ofthe vertical walls 4 a, 4 b of the roof member 1, namely, portions abovethe steps 36 a, 36 a′ and in central portions including the steps 36 a,36 a′, such that the occurrence of twisting in the top plate 2 andbending in the vertical walls 33 a, 33 b is suppressed, as illustratedby the graph in FIG. 13. Note that in the case of the present exemplaryembodiment, stress is reduced throughout the entirety of the verticalwalls 33 a, 33 b in the second pressing process as a result of formingthe steps 36 a, 36 a′ to the vertical walls 33 a, 33 b in the firstpressing process. Note that residual stress as it is referred to in thepresent specification means stress remaining in the material at thepress bottom dead center.

Advantageous Effect 2

Generally, when a non-illustrated pressed component is manufacturedhaving a shape curved along its length direction as viewed from theupper side of a top plate, residual tensile stress is liable to occur invertical walls and flanges at the inside of the curved portion. However,in the case of the present exemplary embodiment, the vertical wall 33 aand the flange 35 a are formed in the first pressing process such thatthe angle DI1 formed between the vertical wall 33 a and the flange 35 aof the intermediate formed component 30 satisfies Equation (5). Thus, inthe present exemplary embodiment, twisting in the top plate 2 is reducedas a result of residual tensile stress being reduced in the verticalwall 4 a and the flange 6 a of the roof member 1. Note that in the caseof the present exemplary embodiment, residual stress at lower portionsof the vertical walls 33 a, 33 b is reduced in the second pressingprocess due to forming the steps 36 a, 36 a′ to the vertical walls 33 a,33 b in the first pressing process.

Advantageous Effect 3

Further, in the case of the present exemplary embodiment, the verticalwall 33 b and the flange 35 b of the intermediate formed component 30are formed in the first pressing process such that the angletherebetween satisfies Equation (6). Thus, in the present exemplaryembodiment, twisting in the top plate 2 is reduced as a result ofresidual compressive stress being reduced in the flange 35 b of the roofmember 1. Note that in the case of the present exemplary embodiment, asillustrated in in FIG. 7A, FIG. 7B, FIG. 7C, and FIG. 7D, theintermediate formed component 30 is pressed in the second pressingprocess such that the vertical wall 33 b and the flange 35 b form thevertical wall 4 b and the flange 6 b of the roof member 1. In suchcases, compressive stress is reduced due to the differences in linelengths of the vertical wall 33 b and the flange 35 b that ariseaccompanying changing the angle between the vertical wall 33 b and theflange 35 b.

Other Advantageous Effect 4

Further, in the case of the present exemplary embodiment, the flange 35b of the intermediate formed component 30 is formed in the firstpressing process by causing a material end of the blank BL to flow inand flexing the blank BL. Thus, in the first pressing process of thepresent exemplary embodiment, the amount of spring-back in the firstpressing process is reduced due to residual compressive stress beingreduced.

The foregoing was an explanation relating to advantageous effects of thepresent exemplary embodiment.

Second Exemplary Embodiment

Next, explanation follows regarding the second exemplary embodiment.First, explanation follows regarding configuration of a roof member 1Aof the present exemplary embodiment illustrated in FIG. 8A, FIG. 8B,FIG. 8C, and FIG. 8D. Explanation then follows regarding configurationof a press apparatus 17A of the present exemplary embodiment illustratedin FIG. 9 and FIG. 10. This will be followed by explanation regarding amanufacturing method of the roof member of the present exemplaryembodiment. This will then be followed by explanation regardingadvantageous effects of the present exemplary embodiment. Note that thefollowing explanation describes portions of the present exemplaryembodiment differing from those of the first exemplary embodiment.

Roof Member Configuration

First, explanation follows regarding configuration of the roof member 1Aof the present exemplary embodiment, with reference to the drawings.Note that the roof member 1A is an example of a pressed component and aspecific pressed component.

As illustrated in FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D, the roofmember 1A of the present exemplary embodiment is not provided with theflanges 6 a, 6 b of the first exemplary embodiment illustrated in FIG.1A, FIG. 1B, FIG. 1C, and FIG. 1D. The roof member 1A of the presentexemplary embodiment has the same configuration as the roof member 1 ofthe first exemplary embodiment with the exception of this point.

Press Apparatus Configuration

Explanation follows regarding the press apparatus 17A of the presentexemplary embodiment, with reference to the drawings. The pressapparatus 17A of the present exemplary embodiment is used to manufacturethe roof member 1A of the present exemplary embodiment.

A first press device 18A of the present exemplary embodiment, asillustrated in FIG. 9, is not provided with the holders 23, 24illustrated in FIG. 2B. Note that the first press device 18A is anexample of a press device. The press apparatus 17A of the presentexemplary embodiment has the same configuration as the press apparatus17 of the first exemplary embodiment with the exception of this point.Note that an intermediate formed component 30A has the sameconfiguration as the intermediate formed component 30 of the firstexemplary embodiment with the exception of the point that the twoflanges 35 a, 35 b are not provided. Namely, the intermediate formedcomponent 30A of the present exemplary embodiment is configured as agutter shaped member.

Roof Member Manufacturing Method

Next, explanation follows regarding a manufacturing method of the roofmember 1A of the present exemplary embodiment. The manufacturing methodof the roof member 1A of the present exemplary embodiment is performedemploying the press apparatus 17A. Moreover, in the manufacturing methodof the roof member 1A of the present exemplary embodiment, a firstpressing process is the same as that of the first exemplary embodiment,with the exception of the point that it is performed using the firstpress device 18A. Note that in the present exemplary embodiment, in thefirst pressing process, the blank BL is pressed by bending to form theintermediate formed component 30A illustrated in FIG. 10.

Advantageous Effect

The present exemplary embodiment exhibits the following advantageouseffects of the first exemplary embodiment: the advantageous effect offirst portion prior contacting, the advantageous effect of being inaccordance with Equation (1), and the Advantageous Effects 1, 2, and 3.

The foregoing was an explanation relating to the second exemplaryembodiment.

Third Exemplary Embodiment

Explanation follows regarding the third exemplary embodiment. First,explanation is given regarding configuration of a roof member 1B of thepresent exemplary embodiment illustrated in FIG. 11A, FIG. 11B, FIG.11C, and FIG. 11D. Next, explanation will be given regardingconfiguration of a press apparatus, not illustrated in the drawings, ofthe present exemplary embodiment. Then, explanation will be givenregarding a manufacturing method of the roof member of the presentexemplary embodiment. This will be followed by explanation regardingadvantageous effects of the present exemplary embodiment. Note that inthe following explanation, explanation will be given regarding portionsof the present exemplary embodiment which differ from those of the firstand second exemplary embodiments. In the explanation of the presentexemplary embodiment, when the reference signs used for components andthe like are similar to the reference signs used for components and thelike in the first and second exemplary embodiments, similar referencesigns are used in the explanation even if not illustrated in thedrawings.

Roof Member Configuration

First, explanation follows regarding configuration of the roof member 1Bof the present exemplary embodiment, with reference to the drawings. Theroof member 1B is an example of a pressed component and a specificpressed component.

As illustrated in FIG. 11A, FIG. 11B, FIG. 11C, and FIG. 11D, the roofmember 1B of the present exemplary embodiment is not provided with theflanges 6 a, 6 b illustrated in FIG. 1A, FIG. 1B, FIG. 1C, and FIG. 1D.Further, a length direction central portion of the roof member 1B of thepresent exemplary embodiment is not curved in the short direction asviewed from the upper side of the top plate 2. Moreover, the roof member1B of the present exemplary embodiment is not curved in a convex profilebowing toward the top plate 2 side as viewed along the short directionof the top plate 2. Configuration of the roof member 1B of the presentexemplary embodiment is similar to that of the roof member 1 of thefirst exemplary embodiment with the exception of these points.

Press Apparatus Configuration

Explanation follows regarding the press apparatus, not illustrated inthe drawings, of the present exemplary embodiment. The press apparatusof the present exemplary embodiment is used to manufacture the roofmember 1B of the present exemplary embodiment.

A first press device and a second press device, not illustrated in thedrawings, of the present exemplary embodiment are, similarly to therespective first press device 18A and the second press device 19 of thesecond exemplary embodiment, not provided with the first holders 23, 24illustrated in FIG. 2B. Further, a groove in the upper mold 21 of thefirst press device of the present exemplary embodiment is formed in astraight line shape that does not curve as viewed along the direction inwhich the upper mold 21 and the lower mold 22 face each other, nor inthe short direction of the upper mold 21 and the lower mold 22. Further,the lower mold 22 projects out in a straight line shape along its lengthdirection. Configuration of the press apparatus of the present exemplaryembodiment is similar to that of the press apparatus 17A of the secondexemplary embodiment with the exception of the points above. Anintermediate formed component, not illustrated in the drawings, formedby a first pressing process of the present exemplary embodiment isconfigured similarly to the intermediate formed component 30A of thesecond exemplary embodiment with the exception of the point that the topplate 2 and the vertical walls 33 a, 33 b are not curved along thelength direction. Namely, the intermediate formed component of thepresent exemplary embodiment is configured by a gutter shaped member.

Roof Member Manufacturing Method

Explanation follows regarding the manufacturing method of the roofmember 1B of the present exemplary embodiment. The manufacturing methodof the roof member 1B of the present exemplary embodiment is the same asthat of the second exemplary embodiment with the exception of the pointthat the press apparatus of the present exemplary embodiment isemployed. Note that in the case of the present exemplary embodiment, ablank BL is pressed by bending to form the intermediate formed componentin the first pressing process.

Advantageous Effects

The present exemplary embodiment exhibits the following advantageouseffects of the first exemplary embodiment: the advantageous effect firstportion prior contacting and the advantageous effect of the verticalwalls 4 a, 4 b being suppressed from closing in due to spring-back, asexplained by the advantageous effect of being in accordance withEquation (1), and the Other Advantageous Effects 1 and 2.

The foregoing was an explanation relating to the third exemplaryembodiment.

EXAMPLES

Explanation follows regarding first, second, and third evaluations inwhich Examples and Comparative Examples were evaluated, with referenceto the drawings. Note that in the following explanation, when thereference signs used for components and the like are similar to thereference signs used for components and the like in the presentexemplary embodiment and the second comparative embodiment, thereference signs for these components and the like are being carried overas-is.

First Evaluation

In the first evaluation, twisting and bending were compared between aroof member 1 configuring Example 1, manufactured by the manufacturingmethod of the roof member of the first exemplary embodiment describedabove, and a roof member configuring Comparative Example 1, manufacturedby the manufacturing method of the roof member of the second comparativeembodiment described above. Further, in the first evaluation, theVickers hardness of the top plate 2 and the convex ridge line portions 3a, 3 b of the roof member 1 of Example 1 and of the roof member ofComparative Example 1 were measured and compared.

Roof Member of Example 1

First, explanation follows regarding the roof member 1 of Example 1. Ahigh tensile sheet steel blank having a plate thickness of 1.2 mm and1310 MPa grade tensile strength was employed as the blank BL. In theroof member 1 of Example 1 manufactured by the manufacturing method ofthe roof member of the present exemplary embodiment, the radius ofcurvature R of the first section 8 was 3000 mm, the radius of curvatureR of the second section 9 was 800 mm, and the radius of curvature R ofthe third section 10 was 4000 mm as viewed from the upper side of thetop plate 2. Further, in the roof member 1 of Example 1, the radius ofcurvature R of the first section 8 was 4000 mm, the radius of curvatureR of the second section 9 was 2000 mm, and the radius of curvature R ofthe third section 10 was 10000 mm as viewed along the short direction ofthe top plate 2, namely, as viewed from the side of a side-face of theroof member 1. Note that in the first pressing process, the bend outersurface stress σ_(s) of the blank BL was 1234 MPa and the average stressσ_(m) was 100 MPa. Further, the Young's Modulus E of the blank BL was208 GPa.

Roof Member of Comparative Example 1

The roof member of Comparative Example 1 was manufactured by themanufacturing method of the roof member of the second comparativeembodiment employing a high tensile sheet steel blank having a platethickness of 1.2 mm and 1310 MPa grade tensile strength as the blank BL,similarly to in Example 1. Note that the roof member of ComparativeExample 1 was manufactured such that each portion of the respectivefirst, second, and third portions would have the same radius ofcurvature R as in Example 1.

Comparison Method

In the comparison method of the present evaluation, first, a 3-dimensionmeasuring device, not illustrated in the drawings, was used to measurethe shapes of the roof member 1 of Example 1 and the roof member ofComparative Example 1. Next, a computer, not illustrated in thedrawings, was used to compare measured data SD for the roof member 1 ofExample 1 and the roof member of Comparative Example 1 against designdata DD. Specifically, as illustrated in FIG. 12, the cross-sections oflength direction central portions of the top plate 2 were aligned(best-fit), and an angle of the top plate 2 along the short direction ata front end (rear end) in the design data DD was taken as a reference,and the amount of change in the angle of the top plate 2 at the frontend (rear end) of each measured data point with respect to thisreference was evaluated as twisting. Further, as illustrated in FIG. 12,the offset amount in the width direction of a center position 02 of afront end face (rear end face) of each measured data point with respectto a center position 01 of the front end face (rear end face) in thedesign data DD was taken as bending.

Comparison Results and Interpretation

The graph in FIG. 13 illustrates evaluation results for Example 1 andComparative Example 1. From the graph in FIG. 13, it is apparent thatthe top plate 2 underwent less twisting in Example 1 than in ComparativeExample 1. Further, from the graph in FIG. 13, it is apparent that thevertical walls 33 a, 33 b underwent less bending in Example 1 than inComparative Example 1. According to the evaluation results above,Example 1 may be considered as exhibiting the advantageous effectsexplained in the first exemplary embodiment.

Vickers Hardness

Further, the graph in FIG. 14 illustrates the results of measuringVickers hardness of the top plate, measured in a range spanning from oneend to another end in the short direction of the top plate 2 of Example1, and the Vickers hardness of the top plate measured in a rangespanning from one end to another end in the short direction of the topplate of Comparative Example 1. The top plate 2 of Example 1 has aVickers hardness value that is smaller than that of the top plate ofComparative Example 1 throughout, namely, over the entirety of a regionspanning from the one end to the other end in the short direction of thetop plate 2. Further, in the case of the top plate of ComparativeExample 1, the value of the Vickers hardness is equal throughout,whereas in the case of the top plate 2 of Example 1, the value of theVickers hardness differs as follows. Namely, in the case of the topplate 2 of Example 1, the top plate 2 includes the central portion wherethe Vickers hardness value is a minimum value at the short directioncenter of the top plate 2, namely, the minimum portion. The top plate 2also includes the maximum portions where the respective Vickers hardnessvalue is a maximum value in each range out of a first range that is therange between the central portion and the one short direction end of thetop plate 2 and a second range that is the range between the centerportion and the other short direction end of the top plate 2. It isthought that the reason the Vickers hardness characteristics of the topplate 2 of Example 1 and the top plate of Comparative Example 1 differfrom each other in this manner is due to the top plate 2 of Example 1having the advantageous effect of being in accordance with Equation (1),namely, the advantageous effect as a result of the Bauschinger effect.Further, as in the evaluation results described above, the roof member 1of Example 1 does not twist, namely, has a smaller spring-back amountthan the roof member of Comparative Example 1. From another perspective,the roof member 1 of Example 1 may be said to be of a higher precisionthan the roof member that includes a top plate having a Vickers hardnessvalue that is equal throughout. Note that as explained above, the reasonfor defining each maximum portion as where the respective Vickershardness value is a maximum value within each range out of the firstrange and the second range, is to indicate that portions where theVickers hardness is a maximum value within each range are not at the twoshort direction ends of the top plate 2. Further, the Vickers hardnessvalue of the central portion, namely, the minimum portion of the topplate 2 of Example 1 is at least 2.3% smaller than the Vickers hardnessvalues of the respective maximum portions.

Second Evaluation

Evaluation Method, Etc.

In the second evaluation, twisting at the front end and the rear end ofthe top plate 2 was evaluated for roof members 1 of Examples 2 to 8produced by simulation based on the roof member manufacturing method ofthe first exemplary embodiment described above, and for roof members ofComparative Examples 2 to 6 produced by simulation based on the roofmember manufacturing method of the second comparative embodimentdescribed above.

The table in FIG. 15 lists the simulation parameters and evaluationresults for Examples 2 to 8 and Comparative Examples 2 to 6. In thetable in FIG. 15, “plate thickness” refers to the thickness of the blankBL that is employed in the simulation. “Strength” refers to the tensilestrength of the blank BL that is used in the simulation. “Shape of topplate portion” refers to there being a curved cross-section profile onthe first mold 20 used in the simulation. The curved cross-sectionprofile in the shape of the top plate portion of the first mold 20 usedin the simulation corresponds to the radius of curvature R in Equation(1) or Equation (2). “Evaluation of cross-section 1 twisting” refers totwisting at a portion 10 mm toward the center from the front end in thelength direction, and “evaluation of cross-section 2 twisting” refers totwisting at a portion 10 mm toward the center from the rear end in thelength direction. Note that each combination of plate thickness,strength, and top plate portion profile in Examples 2 to 8 satisfies theconditions in both Equation (1) and Equation (2). Further, where eachtop plate portion profile is listed as “none” in Comparative Examples 2to 6, this indicates the top plate 2 remaining flat when pressed in thefirst pressing process.

Evaluation Results and Interpretation

From the table in FIG. 15, it is apparent that the top plate 2 underwentless twisting in the roof members of Examples 2 to 8 than in the roofmembers of Comparative Examples 2 to 6. For example, the respectivesimulation parameter for plate thickness and strength were the same inExample 2 and Comparative Example 2. When comparing the simulationresults for evaluation of cross-section 1 twisting, it is apparent thatthe top plate 2 underwent less twisting in the roof member of Example 2than in the roof member of Comparative Example 2. Further, whencomparing the simulation results of evaluation of cross-section 2twisting, it is apparent that the top plate 2 underwent less twisting inthe roof member of Example 2 than in the roof member of ComparativeExample 2. Note that the evaluation of cross-section 2 twisting inExample 2 was −7.52°, with the “−” sign indicating twisting that isclockwise. Thus, it may be said that when comparing the absolute valuesof the angles, the top plate 2 underwent less twisting in the roofmember of Example 2 than in the roof member of Comparative Example 2.Further, when comparing combinations having the same simulationparameters for plate thickness and strength (for example, Example 3 andComparative Example 2, Example 4 and Comparative Example 4, etc.), it isapparent that the top plate 2 underwent less twisting in the respectiveExamples than in the respective Comparative Examples. According to theevaluation results above, Examples 2 to 8 satisfy the conditions inEquation (1) and Equation (2), and thus may be considered as exhibitingthe advantageous effect of being in accordance with Equation (1)irrespective of the differences in tensile strength between the blanksBL.

Third Evaluation

Evaluation Method, etc.

In the third evaluation, twisting at the front end and the rear end wascompared between roof members 1A of Examples 9 to 14 produced bysimulation based on the roof member manufacturing method of the secondexemplary embodiment described above, and for roof members ofComparative Examples 7 to 11 produced by simulation based on the roofmember manufacturing method explained below.

Roof Members of Comparative Examples 7 to 11

The roof members of Comparative Examples 7 to 11 were not provided withthe flanges 6 a, 6 b illustrated in FIG. 1A, FIG. 1B, FIG. 1C, and FIG.1D, similarly to in Examples 9 to 15, namely similarly to the roofmember 1A of the second exemplary embodiment. Thus, the roof members ofComparative Examples 7 to 11 were produced by simulation under theassumption of pressing by bending.

The table in FIG. 16 lists the simulation parameters and evaluationresults for Examples 9 to 14 and Comparative Examples 7 to 11. “Platethickness”, “strength”, “top plate portion profile” “evaluation ofcross-section 1 twisting” and “evaluation of cross-section 2 twisting”in the table in FIG. 16 refer to the same things as in the case of thetable in FIG. 15. Note that the combinations of plate thickness,strength, and top plate portion profile in each of Examples 9 to 14satisfy the conditions in both Equation (1) and Equation (2).

Evaluation Results and Interpretation

From the table in FIG. 16, it is apparent that the top plate 2 underwentless twisting in the roof members of Examples 9 to 14 than in the roofmembers of Comparative Examples 7 to 11. For example, Example 9 andComparative Example 7 had the same simulation parameters for both platethickness and strength. When comparing the simulation results forevaluation of cross-section 1 twisting, it is apparent that the topplate 2 underwent less twisting in the roof member of Example 9 than inthe roof member of Comparative Example 7. Further, when comparing thesimulation results for evaluation of cross-section 2 twisting, it isapparent that the top plate 2 underwent less twisting in the roof memberof Example 9 than in the roof member of Comparative Example 7. Moreover,when comparing combinations having the same simulation parameters forplate thickness and strength, for example, Example 12 and ComparativeExample 10, Example 13 and Comparative Example 11, and so on, it isapparent that the top plate 2 underwent less twisting in each Examplethan in the respective Comparative Example. According to the evaluationresults described above, in the case of Examples 9 to 14, each Examplesatisfies the condition in Equation (1), and thus may be considered asexhibiting the advantageous effect of being in accordance with Equation(1) irrespective of the differences in tensile strength between theblanks BL.

SUMMARY OF EXAMPLES

As explained above, explanation has been given regarding advantageouseffects of the first and the second exemplary embodiments based on thefirst to the third evaluations. However, it is apparent from the secondand third evaluations that the roof members of Examples 2 to 14underwent less twisting than the roof members of Comparative Examples 2to 11, irrespective of the presence or absence of the flanges 6 a, 6 bof the roof member 1. Note that Examples have not been described for thethird exemplary embodiment; however, it is anticipated that there wouldbe less twisting due to the advantageous effect of being in accordancewith Equation (1) in the case of the third exemplary embodiment as well.

As explained above, explanation has been given regarding specificexemplary embodiments of the present disclosure and Examples thereof,namely, the first, second, and third exemplary embodiments and Examples2 to 14. However, configurations other than those of the first, second,and third exemplary embodiments and Examples 2 to 14 described above arealso included within the technical scope of the present disclosure. Forexample, modified examples of the following configurations are alsoincluded within the technical scope of the present disclosure.

In each of the exemplary embodiments, explanation has been given using aroof member as an example of a pressed component. However, the pressedcomponent may be an automotive component other than a roof member aslong as it is manufactured by pressing that satisfies the conditions inEquation (1) or Equation (2). Moreover, the pressed component may alsobe a component other than an automotive component as long as it ismanufactured by pressing that satisfies the conditions in Equation (1)or Equation (2).

In each exemplary embodiment, explanation has been given in which thesteps 11 a, 11 a′ are respectively formed to the vertical walls 4 a, 4b. However, the pressed component may be configured without forming thesteps 11 a, 11 a′ to the vertical walls 4 a, 4 b, as long as the pressedcomponent is manufactured by pressing that satisfies the conditions inEquation (1) or Equation (2).

Explanation has been given in which the manufacturing method of the roofmember of each exemplary embodiment includes the first pressing processand the second pressing process. However, the pressed component need notbe subjected to the second pressing process as long as the pressedcomponent is manufactured by pressing that satisfies the conditions inEquation (1) or Equation (2).

Explanation has been given in which, in the manufacturing method of theroof member of each exemplary embodiment, the intermediate formedcomponent 30 formed by the first pressing process undergoes the secondpressing process so as to manufacture the pressed component. However,since the pressed component is manufactured by pressing that satisfiesthe conditions in Equation (1) or Equation (2), the intermediate formedcomponents 30, 30A described in each exemplary embodiment may beunderstood to be examples of a pressed component. In such cases, thefirst pressing process and the second pressing process may beimplemented by different parties.

Examples of the plate thickness, the tensile strength, the top plateportion profile, and the like of the blank BL were given in theexplanation of each of the exemplary embodiments and in the explanationof the first to third evaluations of the Examples. However, combinationsother than the combinations given as examples in each of the exemplaryembodiments and the Examples may be implemented as long as theparameters of these combinations satisfy the conditions in Equation (1)or Equation (2). For example, even if the tensile strength of the blankBL were more than 1470 (MPa) or were less than 590 (MPa), this would beacceptable as long as the conditions in Equation (1) and Equation (2)were satisfied based on the relationships between the other parameters(σ_(s), σ_(m), E, and so on). Further, for example, even if the platethickness of the blank BL were less than 1.0 mm or were the blank BL tohave a thickness greater than 1.2 mm, this would be acceptable as longas the conditions in Equation (1) or Equation (2) were satisfied basedon the relationships between the other parameters described above.

Explanation has been given in which the roof members 1, 1A, and 1B ofthe respective exemplary embodiments are manufactured by bending a blankBL from the lower mold 22 side toward the upper mold 21 side in a statein which the shoulders 22 d of the lower mold 22 contact the firstportion of the blank BL, before sandwiching the blank BL between theupper mold 21 and the lower mold 22 and indenting the blank BL from theupper mold 21 side toward the lower mold 22 side. Namely, explanationhas been given in which the roof members 1, 1A, and 1B of the respectiveexemplary embodiments are manufactured by forming the first portion ofthe blank BL prior to forming the second portion. However, the pressedcomponent may have a different shape to that of the roof members 1, 1A,and 1B of the present exemplary embodiment as long as the pressedcomponent is manufactured such that the first portion of the blank BL isformed prior to the second portion of the blank BL. For example, thepressed component may be configured with the shapes of the respectivemodified examples described above.

Supplement

The following additional disclosure is a generalization from the presentspecification.

Namely, the additional disclosure is

“A manufacturing method for a pressed component, the manufacturingmethod comprising:

a first pressing performed employing a punch, a die, and a holder tomanufacture a blank into an intermediate formed component having asubstantially hat-shaped lateral cross-section profile configured by atop plate extending in a length direction, two ridge lines respectivelyconnected at both sides of the top plate, two vertical walls connectedto the two respective ridge lines, two concave ridge line portionsconnected to the two respective vertical walls, and two flangesconnected to the two respective concave ridge line portions;

a second pressing performed employing a punch, a die, and a holder tomanufacture the intermediate formed component into a pressed componentthat is a cold pressed component configured from sheet steel having atensile strength of from 440 to 1600 MPa, that has a total length of 500mm or more, and that has a substantially hat-shaped lateralcross-section profile configured by a substantially flat top plate thatextends in the length direction and that has a width of 40 mm or less,two ridge lines respectively connected at both sides of the top plate,two vertical walls that are connected to the two respective ridge lines,two concave ridge line portions connected to the two respective verticalwalls, and two flanges connected to the two respective concave ridgeline portions, wherein

in the first pressing, the top plate of the intermediate formedcomponent is formed into a curved shape such that in a cross-sectionperpendicular to a length direction of the top plate, the top plate isindented toward the inside of the substantially hat-shaped cross-sectionwith a radius of curvature R (mm) as defined in the equation below, and

in the second pressing, the cross-section profile of the top plate ofintermediate formed component is formed into the cross-section profileof the pressed component.

${\frac{t \cdot E \cdot 1000}{2( {\sigma_{s} - \sigma_{m}} )} \times 0.5} \leq R \leq {\frac{t \cdot E \cdot 1000}{2( {\sigma_{s} - \sigma_{m}} )} \times 4}$

wherein the parameters in the equation are as follows:t is a plate thickness (mm) of the blank;σ_(s) is a short direction bend outer surface stress (MPa) of a portionof the blank to form the top plate;σ_(m) is an average stress in cross section of short direction (MPa) ofthe portion of the blank to form the top plate; andE is a Young's Modulus (GPa) of sheet steel configuring the blank.

The disclosures of Japanese Patent Application No. 2015-087502 and No.2015-087503, filed on Apr. 22, 2015, are incorporated in their entiretyby reference herein. All cited documents, patent applications, andtechnical standards mentioned in the present specification areincorporated by reference in the present specification to the sameextent as if the individual cited document, patent application, ortechnical standard was specifically and individually indicated to beincorporated by reference.

1. A pressed component comprising: an elongated top plate; ridge lineportions at both short direction ends of the top plate; and verticalwalls that face each other in a state extending from the ridge lineportions, and the top plate including: a minimum portion where theVickers hardness value is a minimum value between one end and anotherend in the short direction of the top plate, and maximum portions wherethe Vickers hardness value is a maximum value in each range out of afirst range between the minimum portion and the one end, and a secondrange between the minimum portion and the other end.
 2. The pressedcomponent of claim 1, wherein the Vickers hardness value of the minimumportion of the top plate is at least 2.3% smaller than the Vickershardness value of each maximum portion.